The H shaped structure is the pulp, which comprises blood vessels, lymph vessels and nerves. This is the living core of the tooth. It is covered by the dentine, which is a layer of tubes. This is a protective covering, which is also a living tissue. The enamel covers the dentine in turn. This is the hardest substance in the human body. It is a dead tissue and does not regenerate.

Due to bacterial action on deposited food materials, the enamel is broken down. Thus tooth caries or decay begins. This burrows inwards to the dentine. The minute the dentine is affected, it sends warning signals. This is manifested as sensitivity. If ignored by the patient, the decay burrows still deeper, till it reaches the pulp chamber. Now the patient experiences sharp, shooting pain. If left undisturbed, the entire pulp is infected, decayed and broken down. The resulting pus is collected at the base of the root as an abscess. Depending on the severity of the infection the abscess may be large and painful. The pus may permeate into the surrounding bone, causing a big swelling which appears on that side of the face.

The haemoglobin of the broken down blood vessels enters the dentinal tubes and gets deposited there. The iron content of the haemoglobin appears black rendering the tooth discoloured.

Normally the course of treatment will comprise (1) a course of antibiotics and anti-inflammatory drugs and (2) a dental X-ray to visualize the extent of infection.

If the lesion is very large and bone damage is extensive, we decide to extract the tooth. If the pus collection is not very extensive and the bone supports adequate we do a Root Canal Treatment (R.C.T.) to preserve the tooth.

The procedure involves removal of pus through the root canal. This is normally done under local anaesthesia and makes a cavity, which gives us access to the root canals. Once it is done, pulp remnants are removed using specialized instruments. The pus is then allowed to drain, by the capillary pressure method. The pus is removed over 2 to 3 sittings. Once the dentist is satisfied that the pus has been removed the proceeds to the canals. The length of the canal is measured physically and radiographically. The canal is then filled with an inert material and sealed both at the root end and the tooth end. The tooth is then capped with a metallic crown.

The success rate of this treatment is about 80%. Failure of the root canal treatment leads to extraction of the tooth. Failure of R.C.T. manifests as pain, sensitivity or discomfort while chewing. A successfully treated tooth is functional and aids the chewing process. It lasts about eight to ten years, depending on the oral hygiene of the patient.